Chow Mein - noodles with some type of meat and vegetables, eg. chicken. "Special" dishes often have a mixture of chicken, beef, pork, prawn/shrimp.

Sweet & Sour (eg. chicken or pork) - often meat in batter & fried, served with a sharp (vinegar or lemon) but sweet sauce.

Crispy duck - typically shredded duck served with fine strips of vegetables and hoisin sauce, plus thin "pancake" like wraps. You put a bit of everything on a pancake and roll it up, a bit like fajitas.

Crispy beef - typically thin strips of beef battered and fried, served with a sauce.

Dim Sum - small "dumplings", little parcels of veg and meats made with small pancake/flatbread wraps.

First and foremost - authentic, not Americanized and not Canadianized. If it has to be one of the latter two, I'd go with Szechuan. But if the person cannot tolerate spices of any kind, they should stick to Cantonese or something from the north.

We have a rally good local place specializing in Hunan that I love. Contrary to another answer, I'd go Americanized Chinese. Here's the secret. Avoid every place that only has bright pink sweet and sour sauce and no brownish duck sauce. Also, avoid dim sum in China Town, San Francisco. It's authentic, but too expensive for what you get.